South Korean activists sent warm socks and messages attached to balloons toward North Korea Saturday, according to the AFP news agency.
About 1,000 pairs were attached to the five large gas-filled balloons, which were launched in the northern South Korean city of Paju, the AFP reported.
The Seoul-based group North Korea Peace said the messages sent with each pair of socks were "politically innocuous."
"We're not interested in sending political messages or sparking any troubles there. All we want is that people in the North wear warm socks over their frozen feet," Sunny Kim, a spokeswoman for the activists, told AFP.
"Warm socks are so rare and they can easily be traded for cash in the North. One pair of socks fetches about 22 pounds of corn, which is enough to sustain a person for a month," Kim added.
Balloon food, propaganda
Earlier this month, defectors from the North sent packages of food by balloon to their former country ahead of the Lunar New Year.
In December, following the death of North Korean leader Kim Jong il, defectors from the North and southern activists sent giant balloons containing tens of thousands of propaganda leaflets across the border.
The leaflets contained messages opposing another hereditary power transfer in North Korea, as well as portraits of Kim Jong Il and heir Kim Jong Un.
North Korea has warned in the past that it would fire at South Korea in response to such actions.